Electrolysis device

BACKGROUND

The invention relates to an electrolysis device having a plurality of electrolysis cells.

Electrolysis cells, which are used to convert chemical substances into other chemical substances under the action of electricity, are extensively known in the prior art. In general, an electric current is used to bring about a chemical reaction, that is to say substance conversion. This is called electrolysis. A known and widely used form of electrolysis is water electrolysis. In water electrolysis, water is decomposed into its constituents, namely hydrogen and oxygen, using the electric current. In principle, however, other substances may also be subjected to electrolysis, for example carbon dioxide or the like.

These are typically fluid substances that can be fed via corresponding supply conduits to the electrolysis cells in which the actual electrolysis is conducted. The electrolysis products are often likewise in fluid form and are removed from the electrolysis cells via further supply conduits. The supply conduits are generally connected to a cell supply unit that serves to supply the electrolysis cells for operation as intended with the respective substances/at least one operating material. “Supply” here thus means not only feeding of the operating material or of the substance to be electrolyzed but also removal of the respective electrolysis product.

The provision of hydrogen in particular proves to be of industrial interest, especially since hydrogen can be a widely usable energy carrier. Hydrogen can be provided by an electrolysis device, also called an electrolyzer, using renewably generated electrical energy. One possibility for producing hydrogen consists in using an electrolysis device having electrolysis cells that are based on proton exchange membranes (PEMs). The principle of a PEM-based electrolysis device or PEM-based electrolysis cell is known in the prior art, and therefore further explanations in this respect are dispensed with.

SUMMARY

In accordance with an embodiment, an electrolysis device is provided. The electrolysis device includes a plurality of electrolysis cells that are electrically connected in series and are arranged successively at least partly in a stack direction, wherein the series connection is electrically couplable to an electrical energy source, a cell supply unit for supplying the electrolysis cells with at least one operating material and supply conduits connected to the cell supply unit and to opposite ends of the successively arranged electrolysis cells, wherein a negative electric potential of the electrical energy source is electrically couplable to an electric reference potential of the cell supply unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic block diagram of an electrolysis device for the electrolysis of water;

FIG. 2 shows a schematic sectional illustration of a supply conduit of the electrolysis device according to FIG. 1 in the region of an insulating section;

FIG. 3 shows a schematic block diagram like FIG. 1 of a further electrolysis device for the electrolysis of water, in which a cell stack has been divided into four substacks according to a first configuration; and

FIG. 4 shows a schematic illustration like FIG. 3 for a second configuration of the electrolysis device.

DETAILED DESCRIPTION

Generic electrolysis devices generally have a plurality of electrolysis cells that are typically electrically connected in series. The series connection that is formed thereby is electrically coupled to an electrical energy source that provides a suitable electric voltage so that the intended process of electrochemical substance conversion can be implemented by means of the electrolysis cells.

The electrolysis cells are additionally arranged successively in a stack direction so that they form a cell stack. The stacked arrangement makes it possible for the successively arranged electrolysis cells to be directly electrically contacted, meaning that separate electrical connections of the electrolysis cell can be extensively reduced.

Further provided within the cell stack is a supply conduit system (manifold) that serves to feed the at least one operating material to the electrolysis cells and remove it. The operating material may for example comprise the fed fluid, for example water, and/or the reaction product, for example hydrogen and oxygen. The cell stack is generally operated with a certain electrolysis power such that an electric current is as small as possible but an electric voltage is as great as possible. This is achieved by a suitable stacking of the electrolysis cells in the cell stack. As a result, electric voltages at the respective electrolysis cells in the cell stack can add up to the cell stack voltage, while the electrolysis cells connected in series in this way can be operated with an essentially equal current.

The electrolysis power is provided by the energy source, which for this purpose is connectable to respective opposite ends of the cell stack. A multiplicity of electrolysis cells can be arranged in a cell stack, for example more than 100 electrolysis cells, especially several hundred electrolysis cells, but preferably not more than around 400 electrolysis cells. When electrolyzing water to hydrogen and oxygen, an electric voltage at a respective one of the electrolysis cells is around 1.5 V to 2.5 V. The electric voltage at the cell stack correspondingly results from this, meaning that the electric voltage at the cell stack often exceeds 100 V, and may even be several hundred volts.

In addition to the cell stack, the electrolysis device comprises further components, such as for example pumps, heat exchangers, separating vessels, which are required for the operation as intended of the electrolysis device or electrolysis cells. These components are in the present case subsumed under the cell supply unit for supplying the electrolysis cells for operation as intended with at least one operating material.

The cell supply unit is connected to the electrolysis cells arranged successively in a stack direction via supply conduits that are connected at opposite ends of the successively arranged electrolysis cells. The supply conduits are generally formed from a material such as metal or the like.

A correspondingly high electric voltage arises between the ends of the cell stack or of the successively arranged electrolysis cells. For the supply conduits, which are generally formed from a metal, it is therefore necessary for them to have respective electrical insulating sections that serve to avoid an electrically well-conducting connection between the ends of the successively arranged electrolysis cells and hence between the electrical connections of the electrical energy source.

While the use according to the prior art has proven itself in principle, it has been found that corrosion can occur, in particular in the area of the region of the supply conduit which adjoins the electrical insulating section and to which in operation as intended is applied a positive electric potential of the electrical energy source. This is not only harmful for the electrolysis device as such, but may also lead to contaminations of the at least one operating material and hence to disruptions to the intended operation of the electrolysis cells.

In order to reduce this problem, a specific electrical conductivity of the water is kept as small as possible and to kinetically inhibit the corrosion through a maximally long insulation segment or else a cross-sectional reduction in the region of the respective insulating section, and hence to stretch the effect out over time. However, corrosion cannot in principle be avoided thereby. In particular, the ever-present, albeit low, electrical conductivity of water, especially within the insulation segment formed by the insulating section, leads to stray currents in the water, especially within the insulating segment. As a result, the problem of corrosion remains.

With respect to a generic electrolysis device, the invention proposes in particular that a negative electric potential of the electrical energy source is electrically couplable to an electric reference potential of the cell supply unit. Therefore, during operation of the electrolysis device, the negative electric potential of the electrical energy source is electrically coupled to the electric reference potential of the cell supply unit.

In exemplary embodiments, the construction of the electrolysis device makes it possible for the cell supply unit and thus also the end of the cell stack formed by the successively arranged electrolysis cells, which end is connected to the negative electric potential of the electrical energy source, to have the smallest electric potential of the electrolysis device. This end of the cell stack is also denoted “first end” hereinafter.

The electrical connection can be realized by virtue of the first end of the cell stack being connected to the electric reference potential of the cell supply unit by means of an electrical conduit. The electric reference potential of the cell supply unit can for example be a ground potential of the cell supply unit. The electric reference potential of the cell supply unit can for example be indirectly or directly electrically coupled to an earth potential. Moreover, it may of course also be provided that the supply conduits are formed at least partially from an electrically conductive material. In particular, a material of the supply conduits may include metal. It is possible as a result to provide an electrically conductive connection also by means of at least one of the supply conduits, independently of an electrical conduit, specifically if the at least one of the supply conduits provides the electrical conductivity—like the electrical conduit—over its entire length.

It will be appreciated that this of course can apply only for the supply conduits that are connected to the first end of the cell stack. In contrast, at least the supply conduits that are connected to the second end of the cell stack opposite the first end of the cell stack have an insulating section, so that an electrical connection of the second end of the cell stack with the electric reference potential of the cell supply unit is prevented.

If the electrical connection is realized by means of the electrical conduit, all supply conduits can have respective insulating sections, especially when they essentially include metal as material. The supply conduits can, however, also be formed from an electrically insulating material.

In particular, the sections of the supply conduits facing the cell supply unit and up to the respective insulating sections optionally present do not need to have an electric potential that is smaller than the electric potential, especially the electric reference potential, of the cell supply unit. As a result, a corrosion effect can be largely avoided in the region of the supply conduits between the respective insulating sections optionally present and the cell supply unit. The corrosion problem can therefore be shifted to the respectively opposite side of the respective electrical insulating section in the region of which a corresponding supplemental treatment may be provided in order here too to largely avoid or even completely prevent the corrosion effect.

This can be achieved, inter alia, by virtue of the successively arranged electrolysis cells being no longer potential-free with respect to the cell supply unit, but instead it being possible to ensure by way of the inventive construction that the cell supply unit always provides the smallest electric potential in the electrolysis device. The successively arranged electrolysis cells of the cell stack continue to remain electrically connected in series as a whole.

In exemplary embodiments, the corrosive effect can be reduced since the conditions that are detrimental to the corrosive effect can be reduced. Due to the electric potential difference on the insulating sections of the supply conduits, in the prior art an electric current can arise in the fluid conveyed by the respective supply conduit, especially when it is water. Consequently, there may be release of hydrogen and hydroxide ions. The invention makes it possible to reduce the conditions relevant for the corrosive effect, namely in particular the hydroxide ions. In one embodiment, the hydroxide ions can be at least partially processed or consumed in the cell stack by the electrolysis cells disposed there. They are therefore no longer available for the undesired corrosive effect. In one embodiment, the insulating sections are arranged as close as possible in the region of the respective ends. The invention thus makes it possible overall to reduce or even completely avoid the undesired corrosion action.

The electrolysis cells may for example be arranged successively in a single cell stack. In one embodiment, the electrolysis cells are electrically connected in series within the cell stack. The opposite ends of the cell stack, and specifically the first and the second end, are connectable to the respective electric potentials of the electrical energy source. They can for example be directly connected to the electrical energy source. In one embodiment, however, they are connected to the electrical energy source via a control unit, so that the functioning of the electrolysis cells can be set as required.

The electrical energy source can for example be any voltage source or else current source that is able to provide sufficient power for conducting the electrolysis by way of the electrolysis cells. An electrolysis power can be determined for a specific surface current density depending on the dimensions of the respective electrolysis cell, in particular the electrolytically active regions thereof.

The supply conduits have a through-opening having a suitable internal diameter or cross section for allowing the respective operating material to be conducted into the cells in as loss-free a manner as possible and/or to be removed from the respective electrolysis cells or substacks in as loss-free a manner as possible.

It is proposed in one development that a material of the supply conduits includes metal, wherein the electrolysis cells are arranged in at least two substacks, each of the at least two substacks being connected to the cell supply unit by means of at least one first supply conduit connected to the cell supply unit and to a first end of the respective substack and at least one second supply conduit connected to the cell supply unit and to a second end of the respective substack opposite the first end in the stack direction, wherein that first supply conduit which is connected to the first end of that substack that is couplable to a negative electric potential of the electrical energy source is electrically conductively connected to the cell supply unit and all other supply conduits have respective electrical insulating sections.

In one embodiment, the electrolysis cells of the substacks are connected in series, with the respective substacks also being connected in series as a whole. In contrast, in relation to the connection to the cell supply unit, the substacks are in principle essentially fluidically connected in parallel. As a result, a stack voltage on the respective opposite ends of a respective substack can of course be far smaller than the electric voltage that is to be provided on the complete series circuit by the electrical energy source. Here too, the corrosive effect described at the outset can at the same time be reduced or largely avoided.

The electrical insulating sections of the supply conduits are also configured correspondingly, it being possible for these for example to be formed from a suitable material that can be mechanically firmly connected to the respective supply conduit. This may for example involve an annular section arranged at a respective end of a respective supply conduit. The insulating section can of course moreover also be integrated into the supply conduit so that the supply conduit has two mutually electrically insulated supply conduit sections that are separated from one another by the insulating section. In one embodiment, these thus-formed units are connected to one another in fluid-tight fashion, with an essentially constant internal cross section being provided for the respective operating material.

The material provided for the electrical insulating section may for example be a plastic, a ceramic, but also a metal oxide such as for example titanium dioxide, aluminum oxide and/or the like. Furthermore, provision may also be made of a composite material which can for example be formed from a plastic that may for example be fiber reinforced. Of course, provision may also be made of virtually any combinations of these that are selected such that a chemical reaction with the operating material to be respectively conveyed is essentially avoided.

The material of the supply conduit includes at least metal. The metal can for example be a steel, especially a stainless steel. Of course, another metal, for example titanium or the like, may furthermore also be used. Corresponding metal alloys can of course also be provided.

It is proposed in one development that an electrical insulation layer is arranged on the inside of the supply conduit on an insulating section end of the respective insulating section facing the respective end of the respective substack. The insulation layer formed here makes it possible to further reduce the corrosion effect. The electrical insulation layer can for example be formed by a plastic, a ceramic or the like, that is arranged on the inside on the respective supply conduit in the respectively predetermined region. The surface available for the corrosion effects on the inside of the supply conduit can be further reduced as a result.

In one embodiment, the electrical insulation layer extends from the respective insulating section up to the respective end of the respective substack. This can essentially completely avoid a corrosion effect on the supply conduit side. This development therefore makes it possible to further improve the effect of the invention.

It is further proposed that the electrical insulation layer has a coating formed from an insulation material. The coating can for example be formed from a plastic, a paint, a combination thereof and/or the like. The coating can be arranged prior to assembly on the respective supply conduit on the inside in the region of the through-opening of the supply conduit. The coating only needs to extend up to the electrical insulating section. This can achieve a good effect with regard to corrosion protection at limited expense.

It is further proposed that the electrical insulation layer includes a corrosion-resistant metal-containing substance. This can achieve a very robust surface that can be bonded to the supply conduit well.

In one embodiment, the corrosion-resistant metal-containing substance is a metal oxide. The metal oxide can for example be a ceramic material, titanium dioxide, aluminum oxide and/or the like.

It is proposed in one development that the respective ends of the substacks that face the respective insulating sections are electrically insulated from the electrolysis cells. As a result, it can be achieved that the corrosion effect is largely avoided in the region between the insulating section and the respective end of the substack. The effect of the invention can be further improved as a result.

It is further proposed that the cell supply unit is at least indirectly electrically earthed, that is to say the cell supply unit is connectable to an earthing. The cell supply unit with the supply conduits electrically coupled thereto can be connected to a predetermined reference potential by the earthing. As a result of this, the negative potential of the electrical energy source, which is electrically coupled to the cell supply unit via the supply conduits, can at the same time also likewise be indirectly at least earthed. In distinction from the prior art, therefore, the cell stack formed from the substacks is at a defined electric potential with respect to the earth potential and is thus no longer subjected to a floating potential. As a result of this, a defined electric potential difference or electric voltage can thus be achieved on the respective electrical insulating sections. This makes it possible to further improve the functional reliability of the invention.

It is furthermore proposed that the earthing has a sacrificial anode and/or a voltage source, by means of which an electric potential that is negative with respect to the earth potential is applicable to the cell supply unit. This can achieve a “cathodic corrosion protection”. If a voltage source is used, the negative electric potential of the voltage source can be electrically connected to the cell supply unit and to the supply conduits connected thereto. The negative electric potential of the voltage source is likewise correspondingly earthed. For good functioning of the thus-realized corrosion protection, there can be provision that the voltage source provides an electric voltage in a range from around −2 V to around zero volts in relation to the earth potential. In one embodiment, this electric voltage is chosen within a range from around −1 V to around −0.8 V. A corrosion of for example stainless steel can be avoided with an electric voltage chosen within this range, even under maritime conditions, especially in offshore applications. In particular, an external corrosion phenomenon can be reduced or prevented by this.

In order similarly to reduce or avoid an internal corrosion phenomenon, a further electrode in the form of a counter-electrode for cathodic corrosion protection is arranged in the region of the cell supply unit. The internal corrosion phenomenon relates in particular to corrosion effects within the electrolysis device, particularly within the cell supply unit. For example, it may be a titanium electrode, or titanium anode, that may have been coated with a mixed oxide. The thus-formed anode is arranged in a liquid phase of an oxygen separation vessel of the cell supply unit.

In one embodiment, the substacks are connected to the cell supply unit in parallel in terms of supply. In this way, a good supply with the at least one operating material can be achieved for the substacks. The supply can comprise feeding and also removing the operating material or substances produced during the electrolysis.

Supply structures configured in the substacks or electrolysis cells can serve as internal insulation segments. Materials with which for example the water for electrolysis is contacted within a respective substack, excluding in the region of respective active cell areas of the respective electrolysis cells, can satisfy at least one of the following three requirements: the materials are non-metallic; metals to which an electric potential is applied are coated with an oxidation-stable layer, such as for example titanium dioxide, a polymer or the like; and uncoated metals are not electrically connected, that is to say are connected essentially electrically potential-free, in particular floating.

It can thus be achieved with the invention that the electrodes of the active cell areas of the electrolysis cells can act as anodic counter-electrodes. As a result, for example, minimally more oxygen can be formed at respective anodes of the electrolysis cells and minimally less hydrogen can be produced at respective cathodes of the respective electrolysis cells. However, these changes during the electrolysis do not have a significant impact on the efficiency and safety of the electrolysis device. Rather, the advantage of the invention—that no extraneous ions from metallic components can be released due to stray currents—predominates.

The configurations and advantages specified for a respective one of the substacks in principle of course also apply—appropriately adapted—to the entire cell stack when no substacks are formed.

The features and combinations of features stated hereinabove in the description, as well as the features and combinations of features stated hereinafter in the description of the figures and/or shown in the figures alone, are usable not only in the respectively indicated combination but also in other combinations, without departing from the scope of the invention.

The exemplary embodiments elucidated hereinafter are exemplary embodiments of the invention. The features and combinations of features stated above in the description and also the features and combinations of features stated in the following description of exemplary embodiments and/or shown in the figures alone are usable not only in the respectively indicated combination but also in other combinations. Thus, embodiments that are not explicitly shown in the figures and elucidated but which emerge and are producible from the elucidated embodiments by separate combinations of features can also be considered to be encompassed or disclosed by the invention. The features, functions and/or effects presented by means of the exemplary embodiments can represent, each taken alone, individual features, functions and/or effects of the invention that are to be considered independently of one another and which each also independently of one another develop the invention. Thus, the exemplary embodiments are intended to also encompass combinations other than those in the elucidated embodiments. Moreover, the embodiments described can also be supplemented by further already-described features, functions and/or effects of the invention.

FIG. 1 shows a schematic block diagram of an electrolysis device 10, which has a cell stack 54 having a plurality of electrolysis cells 12 that are arranged successively in a stack direction 14. In the present case, the electrolysis cells 12 serve to electrochemically decompose water into its constituents oxygen and hydrogen. The electrolysis device 10 thus in the present case serves to produce hydrogen and oxygen from water.

The electrolysis cells 12 are in the present case arranged directly adjacent to one another so that respective electrodes of the adjacently arranged electrolysis cells 12 can electrically contact. It is provided here that in each case an anode of a first of the electrolysis cells 12 electrically contacts a cathode of the respectively directly adjacently arranged second electrolysis cell 12. The electrolysis cells 12 are electrically connected in series as a result.

Via an internal supply structure (not illustrated further) of the cell stack 54, the electrolysis cells 12 are firstly supplied with water to be electrolyzed and secondly provided with discharge conduits for the substances produced, hydrogen and oxygen. This supply is configured to be connectable to respectively opposite ends 20, 22 of the cell stack 54.

An electrical energy source 16 is further connected at the ends 20, 22 via an electrical conduit 52 and here provides a suitable electric voltage with a suitable electrical power so that the electrolysis cells 12 can be sufficiently supplied with electrical energy for operation as intended.

The electrolysis device 10 further comprises a cell supply unit 18 which serves to supply the electrolysis cells 12 or cell stack 54 with the respective operating materials, which in the present case relates to the feeding of water and the removal of hydrogen and oxygen. The cell supply unit 18 comprises a plurality of components that are required for the operation as intended of the electrolysis device 10, such as for example pumps, heat exchangers, separation vessels and/or the like, these not however being illustrated further here. The cell supply unit 18 is connected to the cell stack 54 in terms of supply via supply conduits 24 that are connected to the cell supply unit 18 and the opposite ends 20, 22 of the cell stack 54. The supply conduits 24 thus fluidically couple the supply structure of the cell stack 54. The supply conduits 24 are in the present case formed from a metal such as stainless steel.

In order to avoid a short circuit between the ends 20, 22 of the cell stack 54 through the supply conduits 24 formed from metal, each of the supply conduits 24 has an electrical insulating section 38. This ensures that the ends 20, 22 are electrically insulated from the cell supply unit 18 and hence are also electrically insulated from one another. The supply conduits 24 are located outside of the cell stack 54.

The insulating sections 38 are in the present case essentially formed from an electrical insulation material that may for example be a suitable ceramic material or else a suitable plastic or composite material.

FIG. 2 shows a schematic sectional view of one of the supply conduits 24 from FIG. 1 in the region of the insulating section 38. FIG. 2 illustrates the supply conduit 24 with a first region 58 that faces the end 22 of the cell stack 54, while an opposite second region 56 faces the cell supply unit 18. The regions 56 and 58 are electrically separated from one another by the insulating section 38. This arrangement is fluid-tight as a whole and has an essentially constant internal diameter 62 through which the relevant fluid can be conveyed—this being water in this case.

Due to the electric voltage present at the electrical insulating section 38, corrosion takes place in a region 64. The reason for this can be considered to be that, in the region of a transition from the region 56 to the electrical insulation section 38, as a result of the water, flowing in the internal diameter 62, accepting electrons from the metal of the wall of the supply conduit 24, negative hydroxide ions are formed that are conveyed to the region 58 by virtue of the electric field and electrochemically react there with the metal of the wall of the supply conduit 24, as illustrated in FIG. 2. As a result, the wall of the supply conduit 24 corrodes in this region 64. This is undesired.

For this kind of corrosion, it should be borne in mind that during operation as intended a DC voltage in a region of several hundred volts can in general be present over the electrical insulating sections 38. This can lead in the region of the electrical insulating section 38 to an excess of electrons in the region 56 and a lack of electrons in the region 58. Due to the magnitude of the electric voltage on the electrical insulating section 38, electrode reactions as previously explained take place from a thermodynamic point of view. While the corrosion effect can be stretched out over time, i.e. kinetically inhibited, by reducing the electric voltage, it cannot be completely suppressed thereby. Even prolonging the insulation segment by means of the electrical insulating section 38 or reducing the internal diameter 62 can only inhibit the corrosion effect in terms of its action, but not avoid it.

In the region 56, the hydrogen formed here may be present dissolved in the water or else in the form of extremely fine bubbles and may be transported away with the water. The amounts produced are in general so small that no disruptive effects result from the hydrogen itself.

However, this does not apply in relation to the hydroxide ions that are present in the water in dissolved form. On account of their negative charge and the direction of the electric field in the region of the electrical insulating section 38, these have a tendency to migrate from the region 56 to the region 58. In this region 58 the metallic material of the supply conduit 24 is then oxidatively decomposed. FIG. 2 illustrates this decomposition for the case in which the supply conduit 24 is formed from stainless steel. However, this effect is not limited to steel, and instead can arise for virtually any other metallic material.

In addition to the release of iron, further metals that may be present in the steel can however also be dissolved. Cations may be formed in this case. On account of their positive charge, the metal cations have the tendency of migrating in the opposite direction to the hydroxide ions. This can result in the occurrence of what is known as rouging from the metal cations, in particular when these are iron ions, and the hydroxide ions. Rouging denotes extremely fine iron-containing particles that can become distributed in the supply conduits 24 and the components of the electrolysis device 10. They can be observed in particular in the supply conduits 24 in which hydrogen is likewise conveyed. If this rouging reaches the oxygen-conveying part of the electrolysis device 10, the rouging can redissolve to form ions.

Cations from the oxygen side can then, inter alia, pass into the electrolysis cells 12 and accumulate there. This process can lead to higher cell voltages and hence lower efficiency of the electrolysis device 10. Mechanisms harmful to the electrolysis cells 12 can also be associated with these cations. For example, hydrogen peroxide formed at the electrodes can on contact with metal ions be converted into radicals that chemically attack a membrane structure of the electrolysis cells 12 and thus can impair the service life of the electrolysis cells 12.

FIG. 3 now shows an electrolysis device 60, with which the aforementioned corrosion effect elucidated on the basis of FIG. 2 can be largely avoided. The following elucidations are based on the elucidations with respect to FIGS. 1 and 2, and reference is therefore additionally made to the statements relating thereto.

As can be seen from FIG. 3, the electrolysis cells 12 are arranged in four substacks 26, 28, 30, 32. Each of the four substacks 26, 28, 30, 32 is connected to the cell supply unit 18 by means of two first supply conduits 24 connected to the cell supply unit 18 and to a first end of the respective substack 26, 28, 30, 32 and two second supply conduits 24 connected to the cell supply unit 18 and to a second end 22 of the respective substack 26, 28, 30, 32 opposite the first end 20 in the stack direction 14. The statements made with respect to FIGS. 1 and 2 essentially apply to the cell supply unit 18.

The first supply conduit 24, which is connected to the first end 20 of that substack 26 that is coupled to a negative electric potential 34 of the electrical energy source 44, is electrically conductively connected to the cell supply unit 18. As a result, precisely this first end 20 of the substack 26 is electrically directly connected to the cell supply unit 18. All other supply conduits 24 have respective electrical insulating sections 38.

There is provision here that the number of electrolysis cells of the substacks 26, 28, 30, 32 is the same for all substacks 26, 28, 30, 32. However, if required this can also be chosen differently in other configurations without departing from the concept of the invention.

The substacks 26, 28, 30, 32 are for their part electrically connected in series so that—from an electrical point of view—a series connection of all electrolysis cells 12 of the substacks 26, 28, 30, 32 is present again—as in the cell stack 54 according to FIG. 1.

As a result of this construction of the electrolysis device 60, it can be achieved that the cell supply unit 18, considered electrically, has the smallest electric potential of the whole electrolysis device 60. This electric potential is further connected to the negative electric potential 34 of the electrical energy source 16. The electrical energy source 16 additionally provides the positive electric potential 36. Between the negative and the positive electric potential 34, 36, the electrical energy source 16 provides the operating voltage for the operation as intended of the electrolysis device 60.

In one embodiment, an electrical insulation layer is configured on the inside of the supply conduit on insulating section ends 40 of the respective insulating sections 38 facing the respective ends 20, 22 of the respective substacks 26, 28, 30, 32, this electrical insulation layer being formed in the present case by a coating of an insulation material. The insulation material is for example a suitable plastic. Alternatively or in addition, however, a corrosion-resistant metal-containing substance may also be provided, for example a metal oxide or the like, especially for example a ceramic material.

There can moreover further be provision that the respective ends 20, 22 of the substacks 26, 28, 30, 32 that face the respective insulating sections 38 are electrically insulated from the electrolysis cells 12. This can further reduce the corrosion effect. In one embodiment, the cell supply unit 18, as illustrated presently in FIG. 3, is electrically earthed by means of an earthing 42.

FIG. 4 shows a schematic illustration like FIG. 3 of a variant of the electrolysis device 60 according to FIG. 3, with only the differences in relation to the configuration according to FIG. 3 being elucidated hereinafter.

There is provision in FIG. 4 that the earthing 42 is not provided directly at the cell supply unit 18 but rather using a voltage source 44, by means of which an electric potential that is negative with respect to the earth potential is applicable to the cell supply unit 18. For this purpose, the voltage source 44 provides an electric voltage of around −1 V to around −0.8 V. However, this voltage can in principle also be chosen for example within a range from around −2 V to around zero volts.

With an electric voltage set in this way, the corrosion effect, for example in stainless steel, can be even better suppressed against corrosion, even under maritime conditions, for example in offshore applications.

In one embodiment, the counter-electrode for the cathodic corrosion protection is then also arranged in the region of the cell supply unit 18. The electrode provided here for the earthing 42 is formed in the present case by a titanium anode that has been coated with a mixed oxide. The titanium anode with the mixed oxide coating is in the present case arranged, electrically insulated from the cell supply unit 18, in a liquid phase of an oxygen separation vessel (not illustrated further).

The exemplary embodiments overall show that the invention can be used to achieve a reduction in the corrosion by virtue of a plurality of substacks 26, 28, 30, 32 of the electrolysis cells 12 being able to be formed that are still all electrically connected in series but are separately connected to the cell supply unit 18 via dedicated supply conduits 24.

As a result of the earthing/grounding concept of the invention, the release of metal ions can be largely prevented. The electrodes of the active cell areas of the electrolysis cells 12 can therefore act as anodic counter-electrodes for stray currents. Undesired corrosion can thus largely be avoided.

The invention is not restricted to application in the electrolysis of water and can equally also be used in other electrolysis operations that are to be conducted, for example a carbon dioxide electrolysis or the like.

The exemplary embodiments serve exclusively for elucidation of the invention and are not intended to restrict it.

Electrolysis device

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